Sterilizing methods



Patented Feb. 17,1953

iSTERILI-ZING METHODS John J. Perkins, Erie, Pa., assignor to AmericanSterilizer Company, Erie, Pa., a corporation of Pennsylvania No Drawing.Application April 6, .1951, Serial No. 219,762

Claims. 1

Some surgical and dental instruments e. g. dental drill heads requireboth sterilization and lubrication. If the instruments are lubricatedbefore sterilization, steam does .not completely destroy the organismsunder the .film of oil or grease. Lubrication after sterilization isobjectionable because itintrocluces an opportunity for contamination.Hot oil bath sterilization requires temperatures much higher than steamsterilizing temperatures and introduces a number of problems. Excessiveamounts of oil are trapped in and do not drain from the instruments. Theoil in the "bath tends to decompose and, to become rancid. There is alsoa fire hazard since the oil bath temperatures approach the fiash point.

This invention is intended to overcome these problems by a steamsterilizing :method which provides a residual film of lubricant at theend of the sterilizing operation.

The instruments to be sterilized and lubricated are first cleaned andwashed by the usual method. This customarily involves the flushing ofthe instruments in a fat solvent such as acetone or .Eitoddard solvent.At the en-d of the washing and cleaning operation, the instruments arecleaned but not sterile and the previous film of lubricant, if any, hasbeen removed. The cleaning and washing technique above described isconventional and other techniques are available.

As an initial step in the sterilizing and lubricating, the cleanedinstruments are precoated, for example by dipping, with a homogeneous oruniform dispersion or mixture of lubricant and water. After draining, ifthe precoating is by dipping, the precoating mixture will uniformly coatall surfaces of the instruments including the depressions, serrations,crevices, locks, joints, bearings, etc. and the surfaces will be inintimate contact or at lea-st contiguous with the water so the organismson the surfaces are not protected by the lubricant.

The precoating mixture of lubricant and water can be selected from alarge class of known materials. The mixture should be non-toxic andnon-corrosive. The lubricant should not break down at the sterilizingtemperatures e. g. 270 F. The wetting properties of the mixture may beimproved by the addition of a wetting agent and by the addition of :asmall amount of detergent. The relative amounts of oil and water are notcritical. Practical mixtures may contain as little as water or as muchas 90% water. Satisfactory mixtures are available commercially ascutting oils which are usually oil-water emulsions 2 with wetting agentand detergent additions. Mixtures of half cutting oil and half water orone-third cutting oil and two-thirds water are satisfactory.

The instruments which have been precoated with'the mixture areplaced ina steam sterilizer and sterilized for a short time by pressure steamsterilization. At 270 F. (27 lbs. per square inch steam pressure) fiveminutes sterilizing time is adequate. In the steam atmosphere, the waterin the mixture is converted to steam thereby effecting moist heatsterilization of organisms on the surfaces of the instruments. Thismoist heat sterilization is effective despite the presence of lubricant.in the mixture. If there were no water in the mixture, the .steam wouldnot be effective at the steam sterilizing temperature as the oil coatingwould protect organisms under the coating. The presence of moisture inthe film with which the instruments are precoated is essential for thesteam sterilization. While the moisture in the precoating film isevaporated during the steam sterilization, the non-volatile lubricantremains on the instruments and at the end of the time necessary toconvert the moisture to steam, there remains only a film of lubricantwhich essentially unaffected by the steam sterilizing atmosphere. .Atthe end of the sterilizing time, the steam is exhausted from thesterilizer and any moisture remaining in the film on the instruments isevaporated as the pressure is reduced due to the heat remaining in theinstruments. Since the sterilizing time is ordinarily only that requiredto convert the moisture in the preco-ating film into steam, thesterilizing takes place quickly and longer sterilizing times arenotuseful.

The simultaneous sterilization and lubrication of the instruments abovedescribed achieves the effectiveness of steam sterilization andeliminates the problems of after lubrication and of oil bathsterilization. Except for the precoating with the lubricant watermixture, the standard steam sterilizing techniques are used so thatthere is no need to train the operators in new techniques. The coatingwith the water-lubricant mixture can conveniently be a rinsing step atthe end of the usual washing and cleaning operations. The instrumentscan be loaded into racks, dipped in a precoating bath, and, afterdraining, loaded directly into the steam sterilizer and thereaftersterilized and simultaneously lubricated by the steam pressuresterilizing technique.

The lubrication obtained by the combined sterilizing and lubricatingmethod is in the form of a uniform film without objectionable excesslubricant. The amount of lubricant can be controlled by varying thepercentage of water in the mixture. Ordinarily a uniform thin film oflubricant is suflicient so that the percentage of water in the mixtureis not critical.

In the case of dental instruments, a suitable flavoring may be added sothat if the instruments contact the patients mouth, the flavoring willcounteract the taste of the lubricant. The flavoring, of course, has noeffect upon the lubrication but has a more pleasing reaction to thepatient.

While the sterilizing and lubricating methods is essentially unaffectedby the quality of the lubricant, the lubricating properties of theresidual film after sterilizing are entirely dependent upon the qualityof the lubricant and the selection of the lubricant is a matter ofengineering opinion and judgment with the resultant diversity ofopinions common in such matters. There are available natural andsynthetic lubricants of varying qualities. The most commonly usednatural lubricants are petroleum base, The most common syntheticlubricants are synthesized or polymerized from hydrocarbons of which theunsaturated open chain hydrocarbons and alcohols are representative. Thesynthetic lubricants for the most part duplicate fractions obtained inpetroleum refining. Both the natural and synthetic lubricants areoiltype lubricants.

in the mixture ranges from a major to a minor 4 percentage suflicient tosubject the instrument surfaces to moist heat sterilization as the waterphase is converted to steam.

3. The method of sterilizing and lubricating surgical instruments andthe like which comprises precoating the instruments with a wet film ofan oil-type lubricant and water mixture selected from the class ofcutting oil emulsions having non-corrosive and non-toxic propertiesincluding oil which is stable against breakdown when subjected tosterilizing steam pressures, and then subjecting the precoatedinstruments with the wet film thereon to a steam pressure atmosphere toconvert the water phase of the mixture to steam and leave theinstruments coated with a'film of lubricant.

4. The method of sterilizing and lubricating surgical instruments andthe like which comprises precoating the instruments with a wet film ofnon-toxic, non-corrosive homogeneous oil-type lubricant and watermixture containing a minor amount of a wetting agent, and thensubjecting the precoated instruments with the wet film thereon to asteam pressure atmosphere to convert the water phase of the mixture tosteam and leave the instruments coated with a film of lubricant.

5. The method of sterilizing and lubricating surgical instruments andthe like which comprises cleaning the instruments with a fat solvent,precoating. the instruments with a homogeneous wet film of non-toxic,non-corrosive oil-type lubricant and water mixture, and then subjectingthe precoated instruments with the wet film thereon to a steam pressureatmosphere to convert the water phase of the mixture to steam and leavethe instruments coated with a film of lubricant.

JOHN J. PERKINS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 763,936 Stilwell June 28, 19042,289,890 Walter July 14, 1942 2,535,365 Marshall Dec. 26, 1950

1. THE METHOD OF STERILLIZING AND LUBRICATING SURGICAL INSTRUMENTS ANDTHE LIKE WHICH COMPRISES PRECOATING THE INSTRUMENTS WITH A WET FILM OFNON-TOXIC, NON-CORROSIVE HOMOGENEOUS OILTYPE LUBRICANT AND WATER MIXTUREAND THAN SUBJECTING THE PRECOATED INSTRUMENTS WITH THE WET FILM THEREONTO A STEAM PRESSURE ATMOSPHERE TO CONVERT THE WATER PHASE OF THE MIXTURETO STEAM AND LEAVE THE INSTRUMENTS COATED WITH A FILM OF LUBRICANT.